There is a book in the DAR Library about Tubb. I copied a number of pages, but most that I copied were from John (the original) down through George, Jr. and his wife, Elizabeth Jane Floyd. It was a quite interesting book.
I do have another Tubb connection through my Grayson family, but that connection is also through George, Jr. A female Grayson married a Petty who had Tubb ancestry.
I have researched with several Tubb descendants in researching my Floyd family.